Occupant protection system having a central unit, sensors and a plurality of control modules which are connected by means of a bus system

ABSTRACT

In occupant protection systems having a large number of sensors and control modules for triggering occupant protection devices, the amount of wiring is significantly increased if they are to be communicatively connected to a central unit. For this reason, bus systems have already been suggested for the control modules for triggering occupant protection devices. In order to further reduce in the wiring, sensors are at least partially integrated into a bus system with additional control modules that are allocated to these sensors. Within the context of a diagnosis process of interrogation and response, which triggers a function test of the control modules for triggering the occupant protection devices, an actual sensor value is sent to the bus system from the control modules of the sensors as a diagnosis response. This response is processed by the central unit and/or the other control modules.

FIELD OF THE INVENTION

The invention relates to an occupant protection system having a centralunit, sensors and a plurality of control modules communicativelyconnected by a bus system for triggering occupant protection devices,especially in motor vehicles.

BACKGROUND INFORMATION

Such occupant protection systems are known, for example from the GermanPatent Publication DE 196 53 794 or DE 196 16 293. These publicationsalso describe the bi-directional data transmission for the diagnosis ofthe control modules, wherein preferably a control information, referredto hereafter as diagnosis interrogation, is sent from the central unitto the control modules. The control modules respond to the interrogationwith a control information or a diagnosis interrogation. This diagnosisoperation serves for cyclical checking of the functional capability andof individual functional parameters of the control modules of theoccupant protection devices.

Previously, the characteristic sensors for occupant protection systems,for example acceleration sensors, have always been connected separatelyand individually with the central unit. In the future, these sensorswill be supplemented by seat occupancy and position sensors, safety beltlock sensors, approach sensors, etc. Conventionally, these sensorstransmit continuously and unilaterally sensor signals to the centralunit. As a result, the effort and expense for wiring and control in thecentral unit, and the number of inputs to the central unit, iscontinuously increasing. An article “Vernetzte Rückhaltesysteme” (LinkedRestraining Systems) by Mr. Bischoff, in the magazineAutomobil-Produktion, June 1997, Issue 3/97, page 84 f., describessensors in a bus system for triggering occupant protection devices, aso-called ignition bus. However, how the sensors were integrated intothe bus system cannot be discerned from the article.

PCT Publication WO 89/09146 discloses on the one hand a sensor databusand on the other hand an actuator databus that are separate from eachother.

Moreover, German Patent Publication DE 195 27 813 C1 discloses, forexample, restraining devices for occupants that provide anacceleration-dependent safety switch which is integrated into theignition system. The central evaluation device can, however, not accessthe data from this sensor and, therefore, cannot use this data fortrigger decisions of other restraining devices. In the diagnosis inquiryprovided for the protection device, only the functional capability isreported back to the central unit. Thus, sensors having universalsignificance for the trigger behavior of the entire occupant protectionsystem cannot be integrated in this manner. As a result, ever moresensors must be provided that are communicatively connected with thecentral unit.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an occupant protectionsystem in which the effort and expense for wiring can be reduced byintegrating sensors into a bus system that connects protection devicemodules to a central control.

This object has been achieved by the combination of the followingfeatures. More specifically, an occupant protection system according tothe invention comprises a central control unit including interrogationmeans for generating interrogation signals, a signal transmittingdatabus connected to said central control unit, a plurality of occupantprotection devices and a corresponding plurality of control modulesarranged in pairs so that each pair comprises one control module and onerespective occupant protection device, said pairs being connectedthrough said signal transmitting databus to each other and to saidcentral control unit for communicating with said central control unitincluding responding to said interrogation signals and for transmittingdiagnosis responses from said protection device to said central controlunit, said system further comprising at least one sensor and at leastone sensor control module forming at least one further pair with said atleast one sensor, wherein said at least one further pair is alsoconnected through said signal transmitting databus to said centralcontrol unit for responding to said interrogation signals andtransmitting a sensor response, whereby said first mentioned pairs andsaid at least one further pair respond to the same said interrogationsignals.

According to the invention there is further provided an occupantprotection system for a vehicle comprising a central control unit, atleast one first sensor for sensing vehicle characteristics, said atleast one first sensor being directly connected to said central controlunit, first pairs of occupant protection devices and respective controlmodules, each first pair comprising an occupant protection device and arespective control module connected to a respective occupant protectiondevice to form said first pairs, a data transmission bus connecting saidfirst pairs to said central control unit and to each other forresponding to interrogation signals from said central control unit, atleast one second pair comprising a sensor control module and an occupantsensor connected to said sensor control module, said data transmissionbus also connecting said at least one second pair to said centralcontrol unit for responding to said interrogation signals from saidcentral control unit, whereby said first mentioned pairs and said atleast one further pair respond to the same said interrogation signals.

According to the invention there is further provided a method foroperating an occupant protection system including a central controlunit, a plurality of occupant protection devices, a plurality ofsensors, and a data transmission bus connecting said occupant protectiondevices to said central control, said method comprising the followingsteps:

(a) dividing said sensors into a first group of sensors and a secondgroup of sensors, said first group of sensors including vehiclecharacteristic sensors, said second group including occupant sensors;

(b) connecting said first group of sensors directly to said centralcontrol independently of said data transmission bus;

(c) connecting said second group of sensors through said datatransmission bus to said central control together with said occupantprotection devices;

(d) generating interrogation signals; and

(e) interrogating said occupant protection devices and said second groupof sensors through said data transmission bus with said interrogationsignals for obtaining diagnosis information from said occupantprotection devices and for obtaining statues information from saidoccupant sensors with the same interrogation signals.

The basic concept of the invention is to interconnect, in addition tothe control modules of the occupant protection devices, the controlmodule or modules of the sensors to each other and to a central unit bya bus system whereby the amount of wiring is significantly reduced. Suchinterconnection is particularly advantageous because the sensors areusually distributed spatially in the vehicle at substantial distancesfrom the central unit. In a multitude of cases, however, the occupantprotection devices themselves are also spatially arranged in theseareas. In part, these occupant protection devices are already groupedtogether as so-called “external assistants”. In that case the sensors,however, are no longer directly connected to the central unit. By makinguse particularly of a bi-directional dialog that has previously beenused for diagnosis of the control modules of the occupant protectiondevices, it is rather simple to link at least certain individual sensorsthrough this bus system to the central unit. This is done according tothe invention by allocating to the sensors corresponding control modulesthat transmit back the actual sensor value as a diagnosis response to adiagnosis interrogation. This approach provides the special advantagethat control modules that are almost identical to those for the occupantprotection devices can be used. Further, the technical softwaretransmission protocol can remain almost unchanged since, with respect tothe protocol, only the number of the control modules increases; thedialog, however, remains externally initially identical.

The processor logic processing can be distributed from the central unitto the individual control modules by providing the control modules ofthe occupant protection devices, in addition to the central unit as isconventionally done, with means that enable them to detect or acquirethe sensor signals transmitted to the bus system as a diagnosisresponse. This feature increases the reaction capability of the controlmodules.

In order to integrate the sensors into the bus system of an occupantprotection system, however, it is necessary that the values to bedetected, are in fact detected or acquired cyclically. The cyclicalrepetition interval, that is, the time duration between two diagnosis orinterrogation cycles for the control module of a sensor, must be takeninto consideration due to the always limited data transmission speed. Amultitude of control modules, for example with sequential multiplexing,leads to an increased number of time windows within a protocolframework. Consequently, the cyclical repetition interval may acquire alength that is not always negligible.

Certain values to be detected, which are important for the occupantprotection system, exhibit a high dynamic characteristic, that is, theyhave a high rate of change as a function of time. For example, theacceleration signals, are very dynamic. Occupant protection systems are,however, particularly time critical because of the brief time spanbetween a first recognizable sensor signal and the time in which theoccupant protection devices must be triggered if they are to providetheir optimal protection effect.

It can therefore be advantageous to integrate only those sensors throughthe control modules into the bus system, which detect values that changerelatively slowly relative to the shortest possible cycle repetitioninterval, or which change, for example, during the non-operative stateof a stationary vehicle.

It is also possible to ensure that all changes are detected by adaptingthe cycle repetition interval to correspond to the rate of change of thevalue to be detected. This must be considered in individual cases, basedon the actual technical conditions.

In a further advantageous embodiment, the diagnosis interrogation ofand/or the response from the control modules of at least individualsensors is suppressed when a control information indicating a safetycritical state, particularly a trigger command, has been sent to atleast one of the control modules.

The invention will be explained in more detail below, with reference toexample embodiments and figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a bus system with control modules for triggering occupantprotection devices and for sensors;

FIG. 2 shows a transmission protocol with broadcast diagnosisinterrogation and symmetrical multiplexing of the individual controlmodules;

FIG. 3 shows a transmission protocol with broadcast diagnosisinterrogation and asymmetrical multiplexing, wherein the control moduleof the sensor responds during every second time window.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BESTMODE OF THE INVENTION

FIG. 1 shows an occupant protection system having a central unit 1,sensors Se and S1 and a plurality of control modules M1, M3, . . . , fortriggering the occupant protection devices I1, I3, . . . The controlmodules M1, M3, . . . are connected, so as to be able to communicate, bymeans of a bus system to one terminal I/Ox of the I/O terminals of thecentral unit 1.

The sensor Se is conventionally connected separately to the central unit1, because this sensor Se detects in an analog manner signals of veryrapidly changing values, such as the acceleration acting on the vehicle.This sensor was not integrated into the bus system in order to assureprocessing of the signal in quasi real-time.

By contrast, the sensor S1, for example a safety belt sensor, changesits condition more slowly or in a time frame that is not critical tosafety, for example, when the vehicle is standing still. This sensor S1is integrated through the control module M2 into the bus system. Thesensor S1 is, for example an occupancy switch sensor and/or a seatbeltsensor. All control modules M1, M2, M3, . . . are preferably allconstructed identically and their respective functions are programmed bysoftware.

In FIGS. 2 and 3 the integration of the sensors into the process ofdiagnosis interrogation and diagnosis response can be particularly wellfollowed. In both figures the diagnosis interrogation 2 of the centralunit 1 is represented as a broadcast interrogation, that is, it goes toall control modules M1, . . . in common. This again shortens theprotocol duration. Basically, however, it is alternatively possible toprovide an individual diagnosis interrogation through the address of thecontrol modules.

The control modules Mx respond to the interrogation 2 with theirrespective diagnosis response 3.Mx. While the response from the controlmodules M1, M3, . . . of the occupant protection devices I1, I2, . . .is primarily only a status information such as defective or notdefective, an actual sensor value of the sensor s1 is sent by thecontrol module M2 to the bus system as the diagnosis response 3.M2 tothe diagnosis inquiry 2. This diagnosis response 3.M2 can be recognizedby the individual control modules M1, M3, . . . of the occupantprotection devices I1, I2, . . . , and by the central unit 1. Thediagnosis response 3.M2 is taken into consideration and, if required,actions can be triggered by the respective control modules. Followingthe diagnosis response 3.M2, all other control modules M3, . . . shownin FIG. 2 then respond until the process is repeated by a reneweddiagnosis interrogation 2 from the central unit 1.

In contrast thereto, the process in FIG. 3 provides for an asymmetricaltime or multiplexing on the bus system. Between the diagnosis responses3.M1, 3.M3, . . . of the control modules M1, M3, . . . of the occupantprotection devices I1, I2, . . . , an actual sensor value s1a, s1b, s1c,. . . of the sensor s1 is sent each time from the control module M2 tothe bus system. Thus, the control module of the sensor s1 responds muchmore frequently, compared to the control modules M1, M3, . . . of theoccupant protection devices I1, I2, . . . The central unit 1 andpossibly also the control modules M1, M3, . . . of the occupantprotection devices I1, I2, . . . thus receive much more rapidly achanging sensor value s1.

Although the invention has been described with reference to specificexample embodiments, it will be appreciated that it is intended to coverall modifications and equivalents within the scope of the appendedclaims. It should also be understood that the present disclosureincludes all possible combinations of any individual features recited inany of the appended claims.

What is claimed is:
 1. An occupant protection system comprising acentral control unit (1) including interrogation means for generatinginterrogation signals, a signal transmitting databus connected to saidcentral control unit, a plurality of occupant protection devices (I1,I2, . . . ) and a corresponding plurality of control modules (M1, M3, .. .) arranged in pairs so that each pair comprises one control moduleand one respective occupant protection device, said pairs beingconnected through said signal transmitting databus to each other and tosaid central control unit for communicating with said central controlunit including responding to said interrogation signals and fortransmitting diagnosis responses from said protection devices to saidcentral control unit, said system further comprising at least one sensor(S1) and at least one sensor control module (M2) forming at least onefurther pair with said at least one sensor (S1), wherein said at leastone further pair is also connected through said signal transmittingdatabus to said central control unit for responding to saidinterrogation signals and transmitting a sensor response, whereby saidfirst mentioned pairs and said at least one further pair respond to thesame said interrogation signals.
 2. The occupant protection system ofclaim 1, wherein said corresponding plurality of control modules (M1,M3), comprises means for evaluating said diagnosis responses from saidoccupant protection devices.
 3. The occupant protection system of claim1, wherein said plurality of control modules (M1, M3) and said at leastone sensor control module (M2) are of identical construction.
 4. Theoccupant protection system of claim 1, wherein said at least one sensor(31) detects an occupant dependent characteristic.
 5. An occupantprotection system for a vehicle comprising a central control unit (1),at least one first sensor (Se) for sensing vehicle characteristics, saidat least one first sensor being directly connected to said centralcontrol unit, first pairs of occupant protection devices and respectivecontrol modules (M1, M2), each first pair comprising an occupantprotection device (I1, I2) and a respective control module (M1, M3)connected to a respective occupant protection device to form said firstpairs, a data transmission bus connecting said first pairs to saidcentral control unit and to each other for responding to interrogationsignals from said central control unit, at least one second paircomprising a sensor control module (M2) and an occupant sensor (S1)connected to said sensor control module (M2), said data transmission busalso connecting said at least one second pair to said central controlunit (1) for responding to said interrogation signals from said centralcontrol unit, whereby said first mentioned pairs and said at least onefurther pair respond to the same said interrogation signals.
 6. Theoccupant protection system of claim 5, wherein said at least one firstsensor (Se) detects signals of rapidly changing values of said vehiclecharacteristics which are transmitted directly to said central controlunit, and wherein said occupant sensor (S1) detects slowly changingoccupant dependent characteristics which are transmitted by said datatransmission bus to said central control unit.
 7. The occupantprotection system of claim 6, wherein said at least one first sensor(Se) is an analog sensor directly connected to said central processingunit for processing said rapidly changing values in quasi real-time. 8.The occupant protection system of claim 5, wherein said first mentionedcontrol modules (M1, M3) and said at least one sensor control module(M2) are of an identical construction.
 9. A method for operating anoccupant protection system including a central control unit, a pluralityof occupant protection devices, a plurality of sensors, and a datatransmission bus connecting said occupant protection devices to saidcentral control, said method comprising the following steps: (a)dividing said sensors into a first group of sensors and a second groupof sensors, said first group of sensors including vehicle characteristicsensors, said second group including occupant sensors; (b) connectingsaid first group of sensors directly to said central controlindependently of said data transmission bus; (c) connecting said secondgroup of sensors through said data transmission bus to said centralcontrol together with said occupant protection devices; (d) generatinginterrogation signals; and (e) interrogating said occupant protectiondevices and said second group of sensors through said data transmissionbus with said interrogation signals for obtaining diagnosis informationfrom said occupant protection devices and for obtaining statusinformation from said occupant sensors with the same interrogationsignals.